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Full text of "Alaskan glacier studies of the National Geographic Society in the Yakutat Bay, Prince William Sound and lower Copper River regions"

826                                ALASKAN GLACIER STUDIES
large striated bowlders and some buried trunks of trees, some of them 15 to 82 inches in diameter. Outside this moraine there are occasional peat rolls and, rarely, duplicate parallel push moraines.
Upon this western lateral moraine are only scattered shrubs including eleven year old alders and younger spruces; but extending down to the very edge of the moraine is a thick, mature, coniferous forest with closely-spaced trees a foot or two in diameter, deep moss and peat, and a luxuriant growth of grasses, forming a striking contrast to the barren zone below. Although the overwhelming majority of trees outside the barren zone are alive, there is an occasional dead tree standing erect, and there are many which were overturned, but not overridden, by the ice edge which formed the lateral moraine. Some of these trees have fallen outward into the forest; some fell toward the ice and rest upon the moraine; and in places there is an inextricable tangle of fallen trunks. The conditions in 1910 vividly recalled those seen a few weeks before along the margins of Columbia Glacier which was then advancing into the forest, as Barry Glacier must have been doing during and just before 1898.
Along the eastern shore of Barry Arm, there is a similar lateral moraine at the edge of the barren zone. It is usually from 6 to 10 feet high, but rises higher where it crosses the mouths of gullies. It extends up to the very edge of thick mature forest, and contains till, gravel, bowlders and wood, as in the case across the fiord. In places this margin has windrows of dead tree trunks, some of them 32 to 40 inches in diameter. On the moraine are young alders, willows, and spruces. We counted the annual rings in one spruce 3 inches in diameter, the largest seen growing on the moraine, and found it to be 11 years old. Outside the moraine were some dead trees still standing erect, and a number of spruces and hemlocks whose tops had been broken off 15 to 26 feet above the ground evidently by ice splinters projecting beyond the lateral moraine, as observed in progress at Columbia Glacier. The broken tree tops lay at the foot of the trunks, which were sometimes inclined and sometimes erect. In several cases the broken tree had sprouted a new top, two or three inches in diameter and always growing erect even on inclined trees. Outside the moraine the forest had thick moss and gave every indication of long, uninterrupted growth. A tree, newly sawed off, which was 22^ inches in diameter had 225 annual rings, suggesting that the fallen trunks which measure 32 to 40 inches in diameter were not less than two centuries and perhaps three or four centuries old. This furnishes a basis for computing the length of time that has elapsed since there has been a glacial advance as extensive as that ending in 1898,
Up to an elevation of 1000 feet this eastern lateral moraine slopes at an average rate of 450 feet to the mile, then flattens to horizontality; ascending again north of Coxe Glacier. The Harriman Expedition photographs and Gilbert's description prove that since the maximum of thin advance there had been sufficient melting so that by 1899 the ice had shrunk away from the edge of the eastern lateral moraine, exposing part of the barren zone.
Within the area occupied in 1899 by the long, narrow, southeastern projection of the glacier a stream from the mountain side had built up an alluvial deposit against the ice edge. This deposit now stands exposed as a terrace, cut into by the stream and with the ice contact slope descending so steeply that some of the gravel has slid down since the supporting ice wall was removed by recession of .the glacier.
On the steeper slopes of both lateral moraines, near the glacier, stones from the outer